The invention relates to methods and knots for attaching a withdrawal cord to a tampon, e.g., a catamenial tampon.
Tampons are typically manufactured by cutting an absorbent material into a desired length, attaching a withdrawal cord to the length of material, forming the length of material into a pledget, and compressing the pledget. The absorbent material may comprise short fibers provided in the form of a nonwoven web, or a bundle of continuous long filaments, i.e., a "filament tow". Filament tow tampons are described in, e.g., U.S. Pat. Nos. 3,177,872, 3,320,956, and 2,934,068. The withdrawal cord has been attached in a number of different ways, e.g., by a row of stitching or by looping the cord over the material and folding or rolling the material around the loop.
One step in the manufacture of filament tow tampons is the knotting of a withdrawal cord at the approximate midpoint of the length of absorbent material. Typically, a length of cord is doubled to form a loop, the doubled cord is passed around the material, and the ends of the cord are drawn through the loop, forming a ring or girth hitch, as shown in FIG. 1.
Canadian Patent 1,163,752 proposes the use of other types of knots, e.g., clove and prussic hitches, to prevent telescoping in spirally wound tampons.
All of these conventional knots are difficult to form in a continuous process, i.e., it is difficult or impossible to form a plurality of knots in a continuous length of cord without cutting or breaking the cord. Accordingly, application of the withdrawal cord tends to be the limiting factor in high speed tampon manufacturing processes.